1. Field of the Invention
This invention relates to an apparatus for needling a nonwoven web, comprising at least one needle beam for carrying at least one needle board, a rocker, which carries the needle beam and comprises at least two parallel arms, which are pivoted to a frame, and a slider-crank mechanism, which is coupled to the rocker or the needle beam, the needle beam and rocker constituting needle board-actuating means.
2. Description of the Prior Art
Needle boards can be driven by slider-crank mechanisms either by means of push rods, which are slidably mounted on slide tracks and to which the needle beams are secured, which carry the needle boards, or by means of rockers, which carry the needle beams and to which the slider-crank mechanisms are pivoted British Patent Specification 1,044,717). The use of a rocker for guiding the needle beams will afford the advantage that the structure is simplified because it is no longer necessary to provide push rods and associated slide tracks between the connecting rods of the slider-crank mechanisms and the rockers. But the provision of a simple rocker requires that the needles are moved along an arc of a circle. Because the length of the rocker levers is large relative to the oscillation amplitude of the rocker, that guidance along an arc will hardly affect the result of the needling operation and may even improve the felting of the nonwoven web in some cases.
In order to permit an influence to be exerted on the result of the needling operation, it is desirable to change the lift of a needle beam which is driven by a slider-crank mechanism. This is generally effected by an adjustment of the eccentricity of the eccentric shaft which carries the connecting rods. That adjustment will also be possible, in principle, if the needle beam is guided by a rocker but this will involve a considerable structural expenditure.